The present invention relates to turbine buckets having an airfoil and a tip shroud carried by the airfoil. More particularly, the invention relates to the internal core profile of a tip shroud carried by an airfoil of a turbine bucket. While the invention is intended in particular for a gas turbine, the use of a scaled design could be applicable to a steam turbine or aircraft engine.
Buckets for turbines typically comprise an airfoil, a platform, a shank and dovetail. The dovetail is secured in a complementary slot in a turbine wheel. Oftentimes, the airfoil includes an integrally formed tip shroud. The buckets including the airfoil and tip shroud are, of course, rotatable about the engine centerline during operation and the airfoil and the tip shroud are located in the hot gas path. Because the tip shroud is mounted at the tip of the airfoil, substantial stresses occur in the tip shroud fillet region between the tip shroud and the airfoil tip. Tip shrouds, whether hollow or solid, are typically designed to balance the mass distribution of the shroud around the top of the airfoil. A benefit of the hollow shroud is that it provides a shroud of reduced weight, but maintains considerable structural stiffness. This results in generally lower stresses in the airfoil-to-tip shroud fillet and improved creep life. Further, certain prior tip shrouds do not cover the airfoil throat, with resultant negative impact on stage efficiency due to flow leakage over the tip shroud.